Value of Seasonal Forecasting Skill

The value of ENSO phase forecasting skill for crop management options was calculated for each ENSO phase with appropriate cropping system and management options. The potential value of optimal use of ENSO phase forecast is evaluated as the mean difference between the returns for optimal cropping system management for each ENSO phase in the time series and returns to all weather optimal cropping system management (Hansen et al. 2001). Inputs like seed and fertilizer cost, crop output prices and fixed costs are considered at the rates prevailing during March 2003, the end of crop season. Results are shown in Tables 17.3 and 17.4.

Table 17.3. Estimated crop yields and value of ENSO phase information for peanut/pigeonpea intercrop system management as compared to all weather optimal sole peanut during 1963-1998 in Anantapur region

ENSO phase

No. of years

Cropping system

Yield by ENSO phase

Value (Rs ha"1)

Peanut (tha"1)

Pigeonpea (tha"1)

(Rsha"1)

El Niño

13

Peanut/SD pigeonpea

0.65

0.21

12000

584

La Niña

11

Peanut/MD pigeonpea

1.22

0.22

19040

7824

Neutral

12

Peanut/SD pigeonpea

0.830

0.35

17080

5664

All years

36

Sole peanut

0.868

-

10416

-

Table 17.4. Estimated crop yields and value of ENSO phase information for sorghum + chickpea crop management as compared to all weather optimal sole chickpea during 1963-1998 in Kurnool region

ENSO phase

No. of years

Cropping system

Yield by ENSO phase

Sorghum Chickpea (tha-1) (tha-1)

(Rsha-1)

Value (Rs ha"1)

El Niño

13

Rainy season sorghum with rabi chickpea

0.67

0.94

12000

160

La Niña

11

Rainy season sorghum with rabi chickpea

1.2

1.0

19040

5 600

Neutral

12

Rainy season sorghum with rabi chickpea

1.1

0.6

17080

(-3200)

All years

36

Sole chickpea

-

1.2

10416

Results and Discussion

ENSO phases have a considerable influence on the seasonal rainfall of Kurnool and Anantapur districts in the scarce rainfall zone of Andhra Pradesh, India. All La Niña phases produced higher rainfall than normal rainfall in both districts in the ensuing monsoon season, and lower rainfall during following monsoon season in all El Niño phases in both districts but for two years in Kurnool (Fig. 17.5a.). Historical crop yields of rainy season sorghum, peanut/pigeonpea intercrops were positively affected by the La Niña phase seasons, indicating that good rainfall distribution leads to higher yields in 50% of the years. Sorghum yield in neutral years is also higher compared to El Niño years (Fig. 17.8). Hence sorghum can be a rainy season crop option except in El Niño years. Contrary to expectations, mungari cotton yielded better in El Niño years compared to neutral or La Niña years. Cotton is a deep rooted and long duration crop with standing moisture stress and solar radiation may the factor favoring in El Niño phases, and it can be a suitable crop option in El Niño years (Fig. 17.9). Peanut and pigeonpea intercrop system is an obvious choice in the light soil areas of Kurnool and Anantapur during the La Niña phase as the median yield for both the crops is conspicuously higher and the yield increase in this phase was >250 kg ha-1 (Figs. 17.10 and 17.12). While chickpea yields were higher in El Niño years, its performance in La Niña was also consistently better than in neutral years (Fig. 17.11a). For Anantapur, ENSO phase wise crop yield analysis indicates that the additive performance of peanut/pigeonpea intercrop system (Fig. 17.12ab) would be higher in La Niña years (>0.9 t ha-1), but low (<0.7 t ha-1) during neutral and El Niño years (Fig. 17.12). Value of ENSO phase forecasting skill (Tables 17.3 and 17.4) has been higher in La Niña phase in both districts at Rs 7564 for peanut median duration pigeonpea in Anantapur and Rs 5 600 for sorghum + chickpea sequential systems in Kurnool. During the El Niño phase, forecasting has the lowest value since optimal crop management with low input applications resulted in low yields as it was limited by moisture availability.

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